1. Field of the Invention
The present invention relates to orthopaedic apparatus for driving and/or removing an orthopaedic screw, and, more particularly, to such orthopaedic apparatus which engage an enlarged head of a bone screw.
2. Description of the Related Art
Elongated fixation members used in orthopaedic applications, such as bone screws or pins, are typically used to fixate or stabilize a portion of a fractured bone relative to another portion of the bone. Known orthopaedic apparatus used to drive and/or remove bone screws or pins engage an end of the bone screw or pin in various ways. For example, some orthopaedic apparatus used to drive bone screws apply an axial force to the end of the bone screw. Illustrative of such apparatus are those disclosed by U.S. Pat. Nos. 4,901,712 (Voegell et al.), 4,423,721 (Otte et al.), and 5,354,292 (Braeuer et al.).
Other orthopaedic apparatus used to drive or remove bone screws apply a radial or sideways force to the end of the bone screw. Illustrative of such apparatus are those disclosed by U.S. Pat. Nos. 4,140,111 (Morrill), 5,139,499 (Small et al.), 4,389,913 (Drouin et al.), and 4,911,154 (Vickers).
Still other orthopaedic apparatus used to drive or remove bone screws use a threaded interconnection between the apparatus and the bone screw. Illustrative of such apparatus are those disclosed by U.S. Pat. Nos. 3,334,624 (Schneider et al.), 4,963,144 (Huene), and 4,995,810 (Soderberg).
Moreover, it is also known to use an orthopaedic apparatus to remove a marrow nail by applying a collar or gripper jaws around a constricted portion of the head of the nail and using a self-tapping rod which threadingly engages the inner end of the hollow, marrow nail. While a securing ring holds the gripper jaws firmly against the constricted portion, it does not provide a radially inward gripping force to the nail. Such an apparatus is disclosed by U.S. Pat. No. 4,981,481 (Kranz et at.). An apparatus such as Kranz et al. could not be used with a bone screw because there is not enough depth in the recess of the head of a bone screw to allow the tapping operation of the apparatus rod.
What is needed in the art is an orthopaedic apparatus which allows reliable removal of an orthopaedic screw or pin.